The use of inorganic or metal powders in injection molding, press and center and in metal injection molding (MIM) processes is a mature technology. Recent developments include the utility of new materials and manufacturing techniques. For example, injection molding and 3D printing uses a variety of inorganic and metallic powders as a raw material from which a variety of product shapes and parts can be made (e.g.) by metal injection molding (MIM) and 3D printing. In particular, precise shapes that perform uses in many commercial and consumer based products have been made. Applications include automotive applications, aerospace applications, consumer durable goods, computer applications, medical applications and others. Inorganic and/or metal powders are consolidated or densified into specific shapes through a number of different production processes.
In general, powder injection molded products are made by obtaining desirable raw materials, such as inorganic, ceramic or elemental or alloy metal powders. These powders can be combined with optional additives, such as resins, waxes, graphite, dyes or lubricants which can be mixed and then formed into an initial shape using hot or cold compaction techniques. Typically, the initially formed shaped material is sintered during the hot compaction stage or after the cold compaction stage to obtain a shaped inorganic or metal object in which the bonds between individual particles form as direct particle to particle bonds. After initial processing, finishing steps including machining, heat treatment, steam treatment, composite formation, plating, etc. can be used in forming a final finished product. Press and Sinter and MIM forming can reduce cost and produce a wide variety of simple and complex finished products in low cost processing techniques.
A substantial need for the improvement of the forming or compaction step has been noted in the industry. The feedstock of the powder material is often difficult to process into the mold or through an orifice useful in 3D printing due to the materials lack of viscoelastic, such as flow characteristics, physical and mechanical properties, and lack of self-ordering and packing of particle fractions. In certain instances, the products made with MIM, Press and Sinter or 3D printing processes do not have the commercially effective physical properties for many applications. Often, the formed objects, green body and/or brown body, have defects such as an absence of strength, density, or other needed properties as a result of insufficient particle packing and subsequent inefficient particle bonding. Further, the energy required to initially conform or eject the particulate mass to a particular shape such that the shape is complete and well-formed is excessive. The machines that initially form or compact the objects do not uniformly or fully fill, the whole space with powder resulting in a malformed part or unit.
Particle and polymer mixtures in which a finely divided powder or particulate is dispersed have been suggested for MIM. Catamold®, a BASF product, is a material for metal and ceramic injection molding based on polyacetal resin combined with stainless steels, special alloys or ceramics. However, Catamold® particulate material is not surface coated and does not have viscoelastic properties or particle packing properties in the resin that are helpful to injection molding and 3D printing processes. U.S. Pat. No. 7,153,594 B2, Kejzelman et. al., discloses organic coatings and lubricants for ferromagnetic chosen from organo-silane, organo-titanate, organo-aluminate or organo-zirconate compounds without a polymer. Without the polymer phase, Kejzelman cannot have viscoelastic properties or particle packing properties.
A substantial need exists to improve powder injection techniques such that the products are improved, the energy to form the part is reduced and the part formed in the process is complete without the malformations.